Previously, we reported that the participatory workplace intervention was effective in reducing stress-related inflammatory markers among 31 Japanese female nurses. During the analysis, we recognized that our intervention might have increased prosocial behaviors like giving social support to others in some participants. Based on this assumption, we ran a secondary analysis, which examined the effect of giving social support on inflammatory markers, autonomic nervous activity (ANA), and perceived job stress (PJS) before and after the intervention. A group of participants who had increased scores on giving social support (n=13) showed significant decreases in interferon-γ, interleukin-6, and interleukin-12/23p40 after the intervention. Another group of those who had decreased/unchanged in the scores (n=17) did not show changes in these markers. Regarding ANA and PJS, no significant changes were observed in both groups. This study presented insight that giving social support at work may provide health benefits towards employees themselves, via decreasing inflammation.